Keyboard operated electrical musical instrument



Feb. 18, 1969 J. A. LIDDALL. 3,427,911

KEYBOARD OPERATED ELECTRICAL MUSICAL INSTRUMENT Filed Dec. 25, 1964 Sheet of 2 FIG. 2 Inventor JACK ANTHONY Ll DDALL by: WKMWz.

Feb. 18, 1969 J. A. LIDDALL 3,427,911

KEYBOARD OPERATED ELECTRICAL MUSICAL INSTRUMENT I FiledDec. 25, 1964 Sheet 2, of 2 2 FIG] UPPER FIG.3

Inventor JACK ANTHONY LIDDALL United States Patent 3,427,911 KEYBOARD OPERATED ELECTRICAL MUSICAL INSTRUMENT Jack Anthony Liddall, Weston, Ontario, Canada, asslgnor of one-half to Junn S. Kashino, Cooksville, Ontario,

Canada Filed Dec. 23, 1964, Ser. No. 420,589

U.S. Cl. 84-1.14 12 Claims Int. Cl. Gh 1/00, 3/00 ABSTRACT OF THE DISCLOSURE A keyboard operated electrical musical instrument having a plurality of electrically conductive, non-magnetlc vibratile members positioned in a magnetic field and in proximity to an inductive transducer whereby movement of the vibratile members in the magnetic field results in the formation of eddy currents in the vibratile members and detection of the eddy currents by the inductive transducer for generation of electrical signals suitable for amplification to drive a loud-speaker.

The invention relates to an electrical musical instrument and is of particular utility in connection with the musical instrument wherein the musical tone is generated by a vibrating metallic member.

In some musical instruments such as a Xylophone or a Vibraphone the musical note is established as striking a metallic bar or tube of a predetermined length and having a natural frequency of vibration corresponding to a predetermined note in the chromatic scale. Many other instruments utilize the principle of vibrating a metallic member to produce a note including for example, an organ, a piano and even stringed instruments such as a guitar. In the case of all of these instruments, and many others which have not been specifically mentioned, various attempts have been made in the past to provide electronic means sensing the various frequencies generated, amplifying the signals detected, and reproducing them through a suitable loud speaker system. However, such prior systems have suffered from two major defects. Thus, in the majority of cases sensing has been achieved by a series of individual electromagnets, each one being placed closely adjacent to its respective vibrating member and sensing the frequency of vibration thereof by means of the well known principle of changing the air gap in the magnetic circuit existing between the electromagnetic and the vibrating member thereby producing an alternating current in the coil. When using this system, it is necessary to provide each individual vibrating member with its own electromagnetic coil each coil being individually connected to the amplifier with resulting complication in the necessary circuit. In addition, when providing a large number of individual coils of this type, it is essential that the coils should be perfectly matched in turns area in order to provide faithful reproduction, The resultant cost is therefore considerable. An additional and further disadvantage however lies in the fact that in this system, the vibrating member must necessarily be of magnetically permeable material, thus virtually restricting the system to ferrous materials such as iron and steel in order to achieve actual magnetic coupling. This limitation eliminates the possibility of using many other highly desirable materials many of which produce more desirable musical characteristics, are free from rust, and are in fact cheaper to manufacture.

Accordingly, it is an objective of the present invention to provide a method and apparatus for the sensing of musical notes which is applicable to a wider range of instruments, which is cheaper to manufacture and which produces a faithful response over a wide range of musical notes and tones.

More particularly, it is an objective of the present 1nvention to provide a method and apparatus having the foregoing advantages which is particularly adapted for use in the sensing of musical notes generated by vibrating conducted members of non-ferrous material.

More particularly, it is an objective of the present invention to provide a method and apparatus having the foregoing advantages wherein a single sensing device may be utilized to sense the vibrations of a large number of vibrating members.

More particularly, it is an objective of the present invention to provide a method and apparatus having the foregoing advantages which is particularly suitable for use with a key board instrument.

More particularly, it is an objective of the present invention to provide a method and apparatus having the foregoing advantages incorporating a variety of controls including a tone control and an adjustable feedback and a vibrato or tremolo control.

The foregoing and other advantages will become apparent from the following description of a preferred embodiment of the invention which is now described by way of example only with reference to the following drawings in which like reference devices refer to like parts thereof throughout the various views and diagrams and in which:

FIGURE 1 is a front elevational view showing a key board musical instrument, similar to a Vibraphone, according to the invention partially cut away to reveal the interior,

FIGURE 2 is a sectional side elevation along the line 2-2 of FIGURE 1;

FIGURE 3 is a block circuit diagram of the electrical components of the embodiments of FIGURES 1 and 2; and

FIGURES 4 and 5 are enlarged details of the portions shown in the phantomed circles 4 and 5 respectively.

From FIGURE 1 it will be noted that this preferred embodiment of the invention comprises a Vibraphone type instrument having a typical casing 10 supported on the floor on feet 11 and having a keyboard generally designated by the arrow 12 covered by the lid 13 hingedly mounted on hinge 14. On the front of casing 10 is the control panel 15 having a volume control 16 and the two vibrato control knobs comprising the speed control knob 17 and intensity control knob 18. Towards the bottom portion of casing 10 foot pedal 19 extends outwardly through slotted openings 20 for foot operation of the damper mechanism to be described below.

Referring now to FIGURE 2 and also the cut away portion of FIGURE 1, it will be seen that actual vibrating members producing the musical notes comprise a series of electrically conductive tubes 21, in this embodiment formed of drawn aluminum of a relatively hard alloy designated as S-T6 cut to predetermined lengths so as to have different natural frequencies of vibration corresponding to the frequency of musical notes in the chromatic scale. Tubes 21 are mounted in spaced parallel relation somewhat in the manner of organ tubes upon wooden cross members 22 extending horizontally across the rear portion of the casing 10 being resiliently supported thereon by means of foam rubber pads 23 and held in posltion by means of pins 24 having rubber casings 24a therearound and passing through oversized holes 25 formed therein to permit unrestricted vibration thereof in use.

The striker mechanism for striking the individual tubes 21 comprises a series of individual such mechanisms located side by side in spaced relation in registration with individual tubes 21, and only one such mechanism will now be described although it will be appreciated that all of the individual mechanisms will be substantially the same. Thus, the striker mechanism comprises a striker or hammer 26 mounted on the free end of hammer arm 27 the other end of which is routed in the hammer pivot bar 28 at an angle thereto. Pivot bar 28 is supported at each end thereof on foam plastic pads 29 formed of polyurethane plastic or the like which are glued or otherwise bonded to cross member 30 fastened by any suitable means to the back and sides of casing 10. Along the upper side of pivot bar 28 there is provided the groove 31 for making pivoting engagement with pivot blade 32 which is itself supported in support bar 33 extending across casing from side to side thereof. A pair of spaced dowel pins 34 are located between each adjacent pair of pivot bars 28 and are routed in support bar and support bar 33 thereby maintaining pivot bar 28 in a predetermined chosen location therealong with hammers 26 in registration with their predetermined individual tubes 21. In order to operate pivot bars 28 a series of keys are provided on keyboard 12 corresponding to the keys of a piano. Thus, a key 35 or 35a (the latter being provided for sharps and flats) comprise wooden strip-like members extending from front to back of casing 10 and mounted on a series of mounting pins 36 and on pivot pins 37. Mounting pins 36 are fastened at predetermined spaced locations along front cross bar 38 and extend into suitable pin recesses formed in the underside of keys 35 and 35a. In addition, felt washers 39 are located around pins 36 for buffering movement of keys 35 and 35a. Pivot pins 37 extend through openings 40 formed in keys 35 and 35a for reception thereof, openings 40 being greatly enlarged throughout the major portion of their length and extending completely through keys 35 and 35a to permit unrestricted pivoting movement thereof. Felt washers 41 are provided around the lower portion of pins 37 which are themselves securely mounted in intermediate cross bar 42. Felt buffers 43 are provided towards the rear end of keys 35 and 35a for buffering downward movement thereof being supported on the upper side of support member 33. Keys 35 and 35a make operative connection with pivot bars 28 for operation of hammers 26 by means of the flexible strip 44 fastened by means of screws 45 and 46 to keys 35 and 35a and to pivot bars 28 respectively, strips 44 being formed of any suitable material such as nylon or cloth webbing or the like.

A damping mechanism is provided for damping vibration of tubes 21 and comprises the continuous foam rubber or plastic strip 47 of generally wedge-shaped cross section extending continuously right across the entire extent of tubes 21 adhesively or otherwise bonded to support member 48 which is itself swingably mounted on mounting plates 49 swingably fastened by screws 50 to the interior of casing 10. Plates 49 are operated by means of connecting rods 51 having an upper end pivotally mounted in plate 49 and a lower end pivotally connected to foot pedal 52, connecting rod 51 passing through oversize opening 53 formed in foot pedal 52 to permit substantial swinging movement relative thereto and being locked in position by means of locking pin 54, which may if desired be comprised by merely bending over the end of connecting rod 51. Foot pedal 52 is provided with a rubber foot or toe plate 55 and is hinged by means of hinge 56 to lower cross member 57 extending from side to side across casing 10. An adjustable stop screw 58 is threadedly located in cross member 57 and makes engagement with buffer plate 59 on foot pedal 52 for adjustably regulating the engagement of damper 47 with tubes 21. A return spring 60 is fastened to support member 48 and tensioned to urge support member 48 and damper 47 normally into engagement with tubes 21.

The electrical pick-up mechanism for sensing vibration of tubes 21 and transducing the same into electrical signals comprises a composite transducer member generally designated as 61 and amplifier 62, a clipper circuit 63 and a loud speaker 64 electrically connected in circuit with one another whereby the essentially sinusoidal electrical signals generated in transducer 61 are amplified in amplifier 62 and optionally subjected to periodic amplitude modulation by the vibrato controls and passed to clipper 63 where they may be optionally subjected to electrical clipping to provide variations in tone by altering wave form from the sinusoidal after which they are communicated to speaker 64. Turning now to transducer 61 it will be seen that this comprises a series of individual ceramic permanent magnets 65 mounted and supported side by side adjacent to one another between upper and lower steel strips 66 which are themselves clamped together by means of bolts 67 passing therethrough at spaced intervals. Magnets 65 are polarized through their thickness that is to say substantially along the axis of bolts 67 with all of the north poles oriented, for example, upwardly and all of the south poles oriented downwardly. In this way, upper and lower steel strips 66 become respectively north and south pole pieces. Strips 66 are somewhat wider along the full extent of their length than magnets 65 and project sideways therefrom as at 68. Sideways projection 68 of strips 66 are each provided with a lengthwise electromagnetic winding of insulated wire, the winding on upper strip 66 being designated as 69 and the winding on lower strip 66 being designated as 70. Windings 69 and 70 constitute very long narrow rectangular coils spaced apart side by side from one another and are connected together in series adding relation, the two ends of which are connected to amplifier 62 as stated above.

In order to provide a simple form of audio feedback to provide sustained notes, both tubes 21 and speaker 64 are mounted on angled back panel 71 forming part or casing 10 whereby vibrations of speaker 64 are transmitted through cross members 22 to tubes 21 and tend to continue vibration of the same long after they would normally have ceased to vibrate.

In operation, the instrument is played somewhat in the general manner of a piano or normal Vibraphone by operation of the keys 35 and 35a. As key 35 for example, is pressed downwardly it will rock about pivot pin 37 thereby drawing web member 44 upwardly and causing pivot bar 28 to pivot about pivot blade 32, one of pads 29 being compressed and the other of pads 29 expanding to accommodate such pivot. Hammer arm 27 and hammer 26 will thereby be swung downwardly and rearwardly into contact with its predetermined respective tube 21 striking the same and causing the same to commence vibrating at its natural frequency. As soon as hammer 26 has completed its striking stroke the key 35 will already have been released by the player thus permitting same to rock upwardly again and web 34 may then swing downwardly and, due to the flexible nature thereof may in fact become flexed and somewhat shortened due to the inertia of pivot bar 28, arm 27 and hammer 26. Very shortly after such downward movement of web 44 pivot bar 28 will rock in the reverse direction in response to the resilience of pads 29 causing arm 27 and hammer 26 to swing forwardly and upwardly away from tubes 21. Since the tube 21 is located close to the permanent magnets 65 and well within the magnetic field thereof eddy currents will be set up in the tube 21, which currents are oscillating in a reversing manner due to the to and fro movement of the tube 21 and such eddy currents will in turn induce secondary signals of an alternating voltage in coils 69 and 70. The secondary signals will be amplified in amplifier 62, such amplification being adjustable to any level desired and may subsequently, if desired, be clipped to vary the tone of the note transmitted and detected and is then passed to speaker 64 for reproduction as an audio wave. Notes reproduced by speaker 64 will cause simultaneous vibration of board 71 which will be communicated through cross bars 22 to tubes 21 tending to vibrate the same. Generally speaking, such feedback vibration will not be sufficient to provide detectible vibration of all tubes 21 but will merely serve to continue the vibration of those tubes 21 which are already vibrating in response to a blow from hammers 26. In order to limit the extent of such feedback damper 47 is maintained normally in contact with tubes 21 by means of tension spring 60, but, where particularly extended notes are required pedal bar 52 may be pressed downwardly by foot of the player thus rocking plate 49 about pivot 50 and moving damper 47 out of contact with tubes 21 thereby permitting the same to continue vibration for a much greater length of time. The precise level of amplification and/or vibrato or tremolo effect can be varied by use of the control knobs 16, 17 and 18.

The signals resulting from several diiferent tubes 21 are all developed in coils 69 and 70 simultaneously, and the coils being connected in series adding relation, such signals are additive and are presented at amplifier 62 as a composite signal.

The foregoing is a description of a preferred embodiment of the invention which is here made by way of example only. The invention is not to be taken as limited to any of the specific features as described but comprehends all such variations as come within the spirit and scope of the following claims.

What I claim is:

1. An electrical musical instrument comprising: a plurality of electrically conductive non-magnetic vibratile members having different frequencies of vibration; means establishing a magnetic field around said conductive members; means operable to selectively vibrate said members in said field and cause the same to vibrate at frequencies corresponding to musical tones and simultaneously excite eddy currents in the said members; inductive pick-up means adjacent said conductive members for sensing said eddy currents and generating electrical signals by induction; and means generating audio signals responsive to said electrical signals.

2. In an electrical musical instrument as claimed in claim 1, means mounting said members in side by side relation adjacent one another and permitting vibrational movement thereof.

3. In an electrical musical instrument as claimed in claim 1, said conductive member formed of a non-ferrous metal.

4. In an electrical musical instrument as claimed in claim 2, said means establishing a magnetic field com prising a plurality of permanent magnets located closely adjacent to and spaced an equal distance from said members for establishing a magnetic field of substantially equal intensity therearound and said inductive pick-up means comprising pick-up coil means mounted in proximity to said magnets and extending substantially transversely of said conductive members and closely adjacent thereto.

5. In an electrical musical instrument as claimed in claim 2, said means for establishing a magnetic field and said inductive pick-up means comprising a plurality of permanent magnets located closely adjacent to and spaced an equal distance from said members and establishing a magnetic field of substantially equal intensity therearound, permeable pole means fastened to said permanent magnets and pick-up coil means mounted on said pole means and extending substantially transversely of said conductive members and closely adjacent thereto.

6. In an electrical musical instrument as claimed in claim 1, said means operable to selectively vibrate said members comprising a plurality of hammers movably mounted adjacent to said members and operable to strike the same selectively.

7. In an electrical musical instrument as claimed in claim 2, said means operable to selectively vibrate said members comprising a plurality of hammers movably mounted adjacent to said members and operable to strike the same selectively, means supporting said hammer in said location, pivot means engaging said supporting means, and flexible resilient pads engaging said supporting means and maintaining the same in engagement with said pivot means.

8. In an electrical musical instrument as claimed in claim 7, manually operable members for selective operation of said hammers.

9. In an electrical musical instrument as claimed in claim 8, link means of predetermined length formed of flexible collapsible material connecting said manually operable members and said supporting means for operation of said hammers.

10. In an electrical musical instrument as claimed in claim 9, a damper member movably mounted adjacent to said conductive members, and linkage connected to said damper member and operable to move the same out of and into contact with said conductive members.

11. In an electrical musical instrument as claimed in claim 10, amplifier means for said electrical signals connected to said pick-up means and a clipper connected to said amplifier means.

12. In an electrical musical instrument as claimed in claim 11, loudspeaker means connected to said clipper means, and a sounding board supporting said conductive members and said loudspeaker means.

References Cited UNITED STATES PATENTS 2,286,587 6/1942 Sundt 84--1.15 2,413,062 12/1946 Miessner 84-1.15 3,229,021 1/1966 Baschet 841.14

FOREIGN PATENTS 835,650 12/1938 France.

ARTHUR GAUSS, Primary Examiner.

ROBERT H. PLOTKIN, Assistant Examiner.

US. Cl. X.R. 84-1.01, 1.15 

